Evolutionary and Physical Properties of Meteoroids

Astrophysical models for meteoroid formation and stellar and planetary evolutions are developed from simulation composition studies

Image-orthicon spectra of Geminids in 1969

The spectra of 25 meteors, recorded with an image orthicon technique in December 1969, are studied in relation to similar records made in August of the same year. Of 19 Geminid meteors in the absolute visual magnitude range 0 to +2, only one showed any evidence of the forbidden line of oxygen at 5577 A, while all Perseid meteors recorded in August exhibited the oxygen line, a result of the large difference in geocentric velocity between the two showers. Atoms identified in faint Geminid meteors include neutral iron, magnesium, calcium and sodium. The molecular bands of nitrogen are also observed

An unusual meteor spectrum

An extraordinary spectrum of a meteor at a velocity of about 18.5 + or - 1.0 km/s was observed with an image orthicon camera. The radiant of the meteor was at an altitude of about 49 deg. It was first seen showing a yellow red continuous spectrum alone at a height of 137 + or - 8 km which is ascribed to the first positive group of nitrogen bands. After the meteor had descended to 116 + or - 6 km above sea level it brightened rapidly from its previous threshold brightness into a uniform continuum, the D-line of neutral sodium appeared, and at height 105 + or - 5 km all the other lines of the spectrum also appeared. The continuum remained dominant to the end. Water of hydration and entrained carbon flakes of characteristic dimension about 0.2 micron or less are proposed as constituents of the meteoroid to explain these phenomena

Vesicle shape, molecular tilt, and the suppression of necks

Can the presence of molecular-tilt order significantly affect the shapes of lipid bilayer membranes, particularly membrane shapes with narrow necks? Motivated by the propensity for tilt order and the common occurrence of narrow necks in the intermediate stages of biological processes such as endocytosis and vesicle trafficking, we examine how tilt order inhibits the formation of necks in the equilibrium shapes of vesicles. For vesicles with a spherical topology, point defects in the molecular order with a total strength of $+2$ are required. We study axisymmetric shapes and suppose that there is a unit-strength defect at each pole of the vesicle. The model is further simplified by the assumption of tilt isotropy: invariance of the energy with respect to rotations of the molecules about the local membrane normal. This isotropy condition leads to a minimal coupling of tilt order and curvature, giving a high energetic cost to regions with Gaussian curvature and tilt order. Minimizing the elastic free energy with constraints of fixed area and fixed enclosed volume determines the allowed shapes. Using numerical calculations, we find several branches of solutions and identify them with the branches previously known for fluid membranes. We find that tilt order changes the relative energy of the branches, suppressing thin necks by making them costly, leading to elongated prolate vesicles as a generic family of tilt-ordered membrane shapes.Comment: 10 pages, 7 figures, submitted to Phy. Rew.

Embedded Micro-Computer Base Force Plate as an Objective Tool to Measure Hoof Lameness Phases in Multiparous Sows

The objective of this study was to compare differences in weight placed on each hoof from sows in differing lameness phases. Twelve, clinically healthy, mixed-parity, crossbred sows (228.89±19.17 kg) were used. The sow was the experimental unit and a cross-over design with a 2 (hind left and hind right hoof) x 3 (days: D-1, D+1 and D+6) factorial arrangement of treatments were compared. On induction day, 10 mg of amphotericin B were injected in the distal interphalangeal joint space in both claws of one hind hoof. All sows served as their own control and treatment. After completion of the first round, sows were given a 7-day rest period and then the round procedures were repeated with the opposite hind hoof induced. Sows stood individually on an embedded force plate for 15 minutes, and weight on each hoof was measured independently. All data were statistically analyzed using the PROC MIXED procedure in SAS. On the D+1, sows exhibited less weight bearing on the induced lame hoof compared to D-1 (P \u3c 0.0001). Regardless of which hoof was injected, sow weight distribution did not vary between the injected left or right hind hooves (P = 0.99) or between rounds (P = 0.64). Findings from our study indicate that the embedded force plate exhibited differences between sound and most lame phases indicating the potential as an objective tool for detecting differences in weight distribution when sows are sound and lame

Evaluation of mechanical and thermal nociception as objective tools to measure painful and nonpainful lameness phases in multiparous sows

The objective of this study was to quantify pain sensitivity differences using mechanical nociception threshold (MNT) and thermal nociception threshold (TNT) tests when sows were in painful and nonpainful transient lameness phases. A total of 24 mixed parity crossbred sows (220.15 ± 21.23 kg) were utilized for the MNT test, and a total of 12 sows (211.41 ± 20.21 kg) were utilized for the TNT test. On induction day (D0), all sows were anesthetized and injected with Amphotericin B (10mg/mL) in the distal interphalangeal joint space in both claws of one randomly selected hind limb to induce transient lameness. Three days were compared: (1) D-1 (sound phase, defined as 1 d before induction), (2) D+1 (most lame phase, defined as 1 d after induction), and (3) D+6 (resolution phase, defined as 6 d after induction). After completion of the first round, sows were given a 7-d rest period and then the procedures were repeated with lameness induced in the contralateral hind limb. During the MNT test, pressure was applied perpendicularly to 3 landmarks in a randomized sequence for each sow: 1) middle of cannon on the hind limb (cannon), 2) 1 cm above the coronary band on the medial hind claw (medial claw), and 3) 1 cm above the coronary band on the lateral hind claw (lateral claw). During the TNT test, a radiant heat stimulus was directed 1 cm above the coronary band. The data were analyzed using the MIXED procedure in SAS with sow as the experimental unit. Differences were analyzed between sound and lame limbs on each day. For the MNT test, pressure tolerated by the lame limb decreased for every landmark (P \u3c 0.05) when comparing D-1 and D+1. The sound limb tolerated more pressure on D+1 and D+6 than on baseline D-1 (P \u3c 0.05). Thermal stimulation tolerated by the sound limb did not change over the 3 d (P \u3e 0.05). However, the sows tolerated less heat stimulation on their lame limb on D+1 compared to D-1 levels (P \u3c 0.05). Both MNT and TNT tests indicated greater pain sensitivity thresholds when sows were acutely lame